Radiometers for the measurement of sunshine duration. Sunshine duration is defined by WMO as the time during which the direct solar radiation exceeds the level of 120 W/m2.
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The Blake-Larsen Sun Recorder is a simple and unique sensor to determine sunshine duration. It detects sunshine duration as the human eye would do by its design and measuring principle. In contrast with present methods, it even determines sunshine duration with dusk and dawn. -
The 96d Campbell-Stokes Pattern Sunshine Recorder employs a glass sphere to focus the sun’s rays to an intense spot, which will char a mark on a curved card mounted concentrically with the sphere.